Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit

Authors

Keith B. Rodenhausen Jr., University of Nebraska-LincolnFollow
Tadas Kasputis, University of Nebraska-LincolnFollow
Angela K. Pannier, University of Nebraska - LincolnFollow
J. Y. Gerasimov, University of Nebraska-Lincoln
R. Y. Lai, University of Nebraska-LincolnFollow
M. Solinsky, The Procter & Gamble Company
T. E. Tiwald, J. A. Woollam Co., Inc.
H. Wang, University of Nebraska-Lincoln
Amitabha Sarkar, Department of Chemical and Biomolecular EngineeringFollow
Tino Hofmann, University of Nebraska - LincolnFollow
Natale J. Ianno, University of Nebraska - LincolnFollow
Mathias Schubert, University of Nebraska - LincolnFollow
Jennifer Y. Gerasimov, University of Nebraska at LincolnFollow

Date of this Version

2011

Citation

REVIEW OF SCIENTIFIC INSTRUMENTS 82, 103111 (2011); doi:10.1063/1.3653880

Comments

Copyright 2011 American Institute of Physics

Abstract

Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing.